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Abstract
Experiments were conducted to evaluate factors affecting persistence of the invasive, federal noxious weed Benghal dayflower in sustainable agronomic systems. Seeds were exposed to a range of temperatures simulating those found in hay bales in the field and periodically tested for viability over 21 days. Seeds were nonviable after one day at 65 °C and after 14 days at 50 or 45 °C. A second series of experiments examined the effects of simulated rumen digestion on germination and viability of Benghal dayflower seeds and the response was compared to that with seeds of five other common weed species. Time courses revealed that seeds from the other weeds were acutely damaged by digestion and viability depressed after 48 and 96 h, but germination of Benghal dayflower seeds was increased at 48 h, and only a slight decrease occurred after 96 h. In the third experimental series, stem fragments of Benghal dayflower were buried in soil at 2 and 6 cm depths and exposed to aerial temperatures of 20, 25, 30, and 35 °C for 30 days. Root development occurred at both depths, but leaf development was restricted at 6 cm and subterranean spathe development was not found at 2 cm. Temperatures higher than 25 °C favor regeneration at both depths. The results, collectively, show the difficulty encountered when trying to control or eradicate Benghal dayflower in sustainable farming systems. Farms must avoid using fresh hay as animal feed when Benghal dayflower is present in hay fields, as little restraint on seed viability will be exerted during digestion and generation of manure. Cultivation is unlikely to be an effective control strategy during summer months when Benghal dayflower is growing most aggressively, because soil temperatures are optimal for vegetative regeneration.
